1902.] HATCHER — OLIGOCENE AND MIOCENE DEPOSITS. 131 



conditions necessary for the deposition and present distribution of 

 the sandstones, clays and conglomerates, together with the preser- 

 vation of remains of the faunas characteristic of each. 



Many have noticed and Prof. J. E. Todd has recorded the 

 presence of great deposits of bones at various localities in the 

 White River beds. He describes them as literally covering the 

 ground in places where they have weathered out over areas 

 frequently of more than an acre in extent. It is not only difficult, 

 but I think impossible to account for these accumulations of bones 

 of terrestrial animals at the bottom and in the very middle of a 

 great lake. Since the surrounding clays are usually almost destitute 

 of bones, it is difficult to understand how the dead carcasses of so 

 many animals were driven or drawn as by a magnet to so limited an 

 area. Accepting the other theory, however, we have seen how 

 during the rainy season the deer, tapirs and other animals are 

 driven to the islands over the flood-plains of the great South 

 American rivers. Since in exceptionally high freshets the lower of 

 these islands become submerged it is not difficult to understand how 

 great numbers of these animals must annually perish, and indeed it 

 is a well-known fact that frequently great numbers of them are 

 caught on low islands and, driven by the rising waters to more 

 limited confines, they are finally all drowned when the island 

 becomes entirely submerged. To such or similar conditions the 

 great deposits of bones in the Oligocene and Miocene deposits of 

 the West may owe their origin. I have frequently observed these 

 deposits, though not covering so great an area as that recorded by 

 Todd, and I have always without exception noted that in the 

 Oligocene beds they occurred in the very fine clays, while in the 

 upper or Miocene deposits they occur in the finer sandstones. 

 Although bones are fairly abundant in the sandstones of all these 

 series of beds, I never observed these extremely rich deposits in the 

 coarse sandstones or conglomerates. 



The above facts, together with those brought forward by Dr. 

 Matthew, have driven me, contrary to my earlier opinion, to reject 

 the theory of a great lake and accept that of small lakes, flood- 

 plains, river channels and higher grass-covered pampas as the 

 conditions prevailing over this region in Oligocene and Miocene 

 times. 



Carnegie Museum, March j/, igo2. 



